arch/arm64/kernel/efi.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Extensible Firmware Interface
   4  *
   5  * Based on Extensible Firmware Interface Specification version 2.4
   6  *
   7  * Copyright (C) 2013, 2014 Linaro Ltd.
   8  */
   9
  10 #include <linux/efi.h>
  11 #include <linux/init.h>
  12 #include <linux/kmemleak.h>
  13 #include <linux/screen_info.h>
  14 #include <linux/vmalloc.h>
  15
  16 #include <asm/efi.h>
  17 #include <asm/stacktrace.h>
  18
  19 static bool region_is_misaligned(const efi_memory_desc_t *md)
  20 {
  21         if (PAGE_SIZE == EFI_PAGE_SIZE)
  22                 return false;
  23         return !PAGE_ALIGNED(md->phys_addr) ||
  24                !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT);
  25 }
  26
  27 /*
  28  * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
  29  * executable, everything else can be mapped with the XN bits
  30  * set. Also take the new (optional) RO/XP bits into account.
  31  */
  32 static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
  33 {
  34         u64 attr = md->attribute;
  35         u32 type = md->type;
  36
  37         if (type == EFI_MEMORY_MAPPED_IO) {
  38                 pgprot_t prot = __pgprot(PROT_DEVICE_nGnRE);
  39
  40                 if (arm64_is_protected_mmio(md->phys_addr,
  41                                             md->num_pages << EFI_PAGE_SHIFT))
  42                         prot = pgprot_encrypted(prot);
  43                 else
  44                         prot = pgprot_decrypted(prot);
  45                 return pgprot_val(prot);
  46         }
  47
  48         if (region_is_misaligned(md)) {
  49                 static bool __initdata code_is_misaligned;
  50
  51                 /*
  52                  * Regions that are not aligned to the OS page size cannot be
  53                  * mapped with strict permissions, as those might interfere
  54                  * with the permissions that are needed by the adjacent
  55                  * region's mapping. However, if we haven't encountered any
  56                  * misaligned runtime code regions so far, we can safely use
  57                  * non-executable permissions for non-code regions.
  58                  */
  59                 code_is_misaligned |= (type == EFI_RUNTIME_SERVICES_CODE);
  60
  61                 return code_is_misaligned ? pgprot_val(PAGE_KERNEL_EXEC)
  62                                           : pgprot_val(PAGE_KERNEL);
  63         }
  64
  65         /* R-- */
  66         if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
  67             (EFI_MEMORY_XP | EFI_MEMORY_RO))
  68                 return pgprot_val(PAGE_KERNEL_RO);
  69
  70         /* R-X */
  71         if (attr & EFI_MEMORY_RO)
  72                 return pgprot_val(PAGE_KERNEL_ROX);
  73
  74         /* RW- */
  75         if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
  76              EFI_MEMORY_XP) ||
  77             type != EFI_RUNTIME_SERVICES_CODE)
  78                 return pgprot_val(PAGE_KERNEL);
  79
  80         /* RWX */
  81         return pgprot_val(PAGE_KERNEL_EXEC);
  82 }
  83
  84 int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
  85 {
  86         pteval_t prot_val = create_mapping_protection(md);
  87         bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
  88                                    md->type == EFI_RUNTIME_SERVICES_DATA);
  89
  90         /*
  91          * If this region is not aligned to the page size used by the OS, the
  92          * mapping will be rounded outwards, and may end up sharing a page
  93          * frame with an adjacent runtime memory region. Given that the page
  94          * table descriptor covering the shared page will be rewritten when the
  95          * adjacent region gets mapped, we must avoid block mappings here so we
  96          * don't have to worry about splitting them when that happens.
  97          */
  98         if (region_is_misaligned(md))
  99                 page_mappings_only = true;
 100
 101         create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
 102                            md->num_pages << EFI_PAGE_SHIFT,
 103                            __pgprot(prot_val | PTE_NG), page_mappings_only);
 104         return 0;
 105 }
 106
 107 struct set_perm_data {
 108         const efi_memory_desc_t *md;
 109         bool                    has_bti;
 110 };
 111
 112 static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
 113 {
 114         struct set_perm_data *spd = data;
 115         const efi_memory_desc_t *md = spd->md;
 116         pte_t pte = __ptep_get(ptep);
 117
 118         if (md->attribute & EFI_MEMORY_RO)
 119                 pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
 120         if (md->attribute & EFI_MEMORY_XP)
 121                 pte = set_pte_bit(pte, __pgprot(PTE_PXN));
 122         else if (system_supports_bti_kernel() && spd->has_bti)
 123                 pte = set_pte_bit(pte, __pgprot(PTE_GP));
 124         __set_pte(ptep, pte);
 125         return 0;
 126 }
 127
 128 int __init efi_set_mapping_permissions(struct mm_struct *mm,
 129                                        efi_memory_desc_t *md,
 130                                        bool has_bti)
 131 {
 132         struct set_perm_data data = { md, has_bti };
 133
 134         BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
 135                md->type != EFI_RUNTIME_SERVICES_DATA);
 136
 137         if (region_is_misaligned(md))
 138                 return 0;
 139
 140         /*
 141          * Calling apply_to_page_range() is only safe on regions that are
 142          * guaranteed to be mapped down to pages. Since we are only called
 143          * for regions that have been mapped using efi_create_mapping() above
 144          * (and this is checked by the generic Memory Attributes table parsing
 145          * routines), there is no need to check that again here.
 146          */
 147         return apply_to_page_range(mm, md->virt_addr,
 148                                    md->num_pages << EFI_PAGE_SHIFT,
 149                                    set_permissions, &data);
 150 }
 151
 152 /*
 153  * UpdateCapsule() depends on the system being shutdown via
 154  * ResetSystem().
 155  */
 156 bool efi_poweroff_required(void)
 157 {
 158         return efi_enabled(EFI_RUNTIME_SERVICES);
 159 }
 160
 161 asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
 162 {
 163         pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
 164         return s;
 165 }
 166
 167 static DEFINE_RAW_SPINLOCK(efi_rt_lock);
 168
 169 void arch_efi_call_virt_setup(void)
 170 {
 171         efi_virtmap_load();
 172         __efi_fpsimd_begin();
 173         raw_spin_lock(&efi_rt_lock);
 174 }
 175
 176 void arch_efi_call_virt_teardown(void)
 177 {
 178         raw_spin_unlock(&efi_rt_lock);
 179         __efi_fpsimd_end();
 180         efi_virtmap_unload();
 181 }
 182
 183 asmlinkage u64 *efi_rt_stack_top __ro_after_init;
 184
 185 asmlinkage efi_status_t __efi_rt_asm_recover(void);
 186
 187 bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg)
 188 {
 189          /* Check whether the exception occurred while running the firmware */
 190         if (!current_in_efi() || regs->pc >= TASK_SIZE_64)
 191                 return false;
 192
 193         pr_err(FW_BUG "Unable to handle %s in EFI runtime service\n", msg);
 194         add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
 195         clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
 196
 197         regs->regs[0]   = EFI_ABORTED;
 198         regs->regs[30]  = efi_rt_stack_top[-1];
 199         regs->pc        = (u64)__efi_rt_asm_recover;
 200
 201         if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK))
 202                 regs->regs[18] = efi_rt_stack_top[-2];
 203
 204         return true;
 205 }
 206
 207 /* EFI requires 8 KiB of stack space for runtime services */
 208 static_assert(THREAD_SIZE >= SZ_8K);
 209
 210 static int __init arm64_efi_rt_init(void)
 211 {
 212         void *p;
 213
 214         if (!efi_enabled(EFI_RUNTIME_SERVICES))
 215                 return 0;
 216
 217         p = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, GFP_KERNEL,
 218                            NUMA_NO_NODE, &&l);
 219 l:      if (!p) {
 220                 pr_warn("Failed to allocate EFI runtime stack\n");
 221                 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
 222                 return -ENOMEM;
 223         }
 224
 225         kmemleak_not_leak(p);
 226         efi_rt_stack_top = p + THREAD_SIZE;
 227         return 0;
 228 }
 229 core_initcall(arm64_efi_rt_init);